The subject invention generally relates to image copying, and more particularly techniques for efficiently scanning an image multiple times to make multiple copies.
Digital copiers commonly include a scanner section that optically scans a scan region that contains a source image to be copied or reproduced and provides a scan data output that is a digitized representation of the scan region, an image processor that processes the scan data and generates print data, a print buffer memory for buffering the print data output of the image processor, and a printer section for printing the print data.
A straightforward way to make multiple copies of a particular image with the foregoing digital copier structure is to scan the scan region once, store the print data in the print buffer memory, and then repeatedly print the buffered print data. However, this technique requires sufficient memory to store the print data for the entire scan region, which increases the cost of the copier.
A simple technique of making multiple copies with a digital copier that does not have sufficient memory to store all of the print data for an entire scan region would be to repeatedly scan the entire scan region a number of times as required. This, however, would be time consuming. Time is further consumed, in the form of processor bandwidth, by requiring the processor to move wider pieces of data from the image processor section to the print buffer. Time is also consumed as a result of scanner stalls which occur when the print buffer fills because the image processor typically produces print data faster than the print section utilizes the print data. Scanner stalls also degrade print quality by producing a slight overlap or gap between printed areas that correspond to image regions that were scanned before and immediately after a scanner stall.
It would therefore be an advantage to provide an improved technique of making multiple copies of an image.
The foregoing and other advantages are provided by the invention in a method of making multiple copies of an image that includes the steps of (a) scanning a scan region that contains the image to be copied to produce an array of scan region pixel data that contains pixel data for the entire scan region; (b) printing an image based on the array of scan region pixel data; (c) analyzing scan region pixel data to determine a subregion of the scan region that contains printable, non-background information; (d) scanning the subregion of the scan region to produce an array of print data that contains print data only for the subregion of the scan region that contains printable, non-background information; and (e) printing an image based on the subregion print data.